A variety of processes contact finely divided particulate material with a hydrocarbon feedstock under conditions to fluidize the particulate material to affect transport of the particulate material to different stages of the process. Such processes commonly employ a subsequent stripping operation to remove at least some of the gaseous hydrocarbons that have become adsorbed and/or entrained within the particulate material. One example is fluid catalytic cracking (FCC) of hydrocarbons. FCC of hydrocarbons is a primary refinery process for the production of gasoline and light hydrocarbon products from heavy hydrocarbon charge stocks such as vacuum gas oils or residual feedstock.
The basic equipment utilized in the fluid catalytic cracking of hydrocarbons includes a reactor, a regenerator, and a catalyst stripper. The reactor includes a reaction or contact zone and a separation zone. In the contact zone, a hydrocarbon feed material, e.g., oil, is contacted with a catalyst made up of a finely divided or particulate solid material. The catalyst for the reaction is transported like a fluid by passing gas or vapor through the catalyst at sufficient velocity to produce a desired regime of fluid transport. Contact of the oil with the fluidized particulate material promotes the cracking reactions. As the cracking reactions proceeds, substantial amounts of carbonaceous material, called coke, is deposited on and deactivates the catalyst (commonly referred to herein as “spent catalyst”). In the separation zone, product vapors from the cracking reaction are separated from the catalyst. Further product separation takes place in the catalyst stripper that receives catalyst from the separation zone and removes trapped gaseous hydrocarbons from the catalyst by countercurrent contact with an inert stripping medium. The catalyst is circulated to the regenerator section that includes a regeneration zone where high temperature regeneration of the catalyst occurs by burning coke from the catalyst in the presence of oxygen. Spent catalyst is continually removed from the reaction zone and replaced by essentially coke-free catalyst from the regeneration zone.
A common method of stripping catalyst in the FCC of hydrocarbons or other similar processes includes passing an inert stripping gas, such as or typically steam, countercurrent through a flowing stream of catalyst. Such steam stripping operations, with varying degrees of efficiency, remove the hydrocarbon vapors that are adsorbed on and/or entrained with the catalyst. The efficiency of catalyst stripping is typically increased by employing structured packing that includes vertically spaced baffles to cascade the catalyst from side to side as it moves down the catalyst stripper and countercurrently contacts a stripping medium. Moving the catalyst from side to side increases both the residence time and contact between the catalyst and the stripping medium so that more hydrocarbons are stripped from the catalyst. In such structured packing, the catalyst and stripping medium travel a labyrinthine path through a series of baffles located to affect two-phase mixing. Catalyst and gas contact is increased by this arrangement that leaves no open vertical path for single phase flow through the stripping apparatus. The structured packing includes rows of baffles that are typically secured in position with reinforcing rods some of which are secured to the lower sections of the baffles.
Accordingly, it is desirable to provide apparatuses and processes for stripping gaseous hydrocarbons from particulate material that provide high stripping efficiency. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.